1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus in which a thermal printing head applies heat to both sides of a medium to print images.
2. Description of the Related Art
In order to print images on both sides of a medium, it is possible to equip an image forming apparatus with two thermal printing heads (TPHs). The thermal printing heads (TPH) face first and second surfaces of a medium, respectively. However, the cost of such an image forming apparatus is relatively high.
A method in which first and second surfaces of a medium sequentially faces a TPH can be considered. In this case, two methods can be considered. In one method, a TPH is fixed and a medium is reversed. In another method, a TPH is sequentially moved to locations which face the first and second surfaces of a medium. U.S. Pat. No. 6,296,405 discloses an image forming apparatus formed by combining the methods described above. A TPH is installed in a rotation bracket. The rotation bracket moves between first and second positions on a pivot shaft. When a medium passes the first position, printing to a first surface is performed. After the medium is transferred from the first position to the second position, printing to a second surface is performed. U.S. Pat. No. 6,601,952 discloses an image forming apparatus to which another method is applied. A rotation unit is formed of a TPH, a supporting element to press a medium to the TPH, and a holder supporting a medium. The rotation unit is rotated, thereby facing the TPH to first and second surfaces of the medium.
Accordingly, there is a need for an improved image forming apparatus in which a thermal printing head applies heat to both sides of a medium to print images.